The present invention relates to apparatus for automatically watering a lawn or agricultural area, humidifying a space such as a room, or adding water to a pool when needed, which turns on to permit the flow of water when a moisture sensing element placed at the location to be supplied with water senses a dry condition There is no requirement for any electrical power supply.
A number of automatic watering and irrigation systems have been devised. The most common of these is used for watering lawns and is set by clocks or timers. Such a device is activated by an electrical solenoid controlled valve, which is activated at predetermined times for set intervals of time. Such systems, however, turn the water supply on even if there is no need for watering, such as when it is raining, and shut off even if the place to be watered has been insufficiently watered. Such systems require a costly electrical timing system and a power supply.
The electrical systems are subject to electrical failures, shorting of the power supply, and damage to the solenoids. Attempts have been made in the prior art to overcome these major disadvantages. The non-electrical systems are unreliable.
In the patent to Beckman, U.S. Pat. No. 4,214,701, a swellable member is clamped around a water supply hose. When wet, the member swells to cut off the flow of water by crimping the hose. However, such action is unreliable, inaccurate and could not be used in place of the existing water sprinkling systems typically found in the home environment.
In the patent to Gibson, U.S. Pat. No. 3,874,590, the swelling of a member, when wet, results in the opening or closing of a switch. The control valve is installed in the ground and requires a complicated arrangement of openings and closings. The presence of the entire device in the ground is undesirable and since it requires physical changes in dimension of an object to operate, the operation of the valve is unreliable.
In U.S. Pat. No. 2,445,717, a ceramic element positioned below a sealed vertical tube filled with water is buried in the soil. A pressure sensitive diaphragm is provided at the top of the tube and operates a valve which controls the irrigation system. When the soil surrounding the ceramic body is dry, the water seeps out into the soil creating a low pressure area in the tube above the water and creates a pressure differential above the diaphragm, thereby turning on the water. When the soil is saturated, the flow of water reverses and the pressure on the diaphragm is once again balanced, closing the valve. This device requires the water in the tube to be periodically replenished and the device must be accessible to the surface for periodic maintenance. The pressure differential created is relatively small and accordingly, the reliability of the device is limited.
In the device shown in the patent to Treirat, U.S. Pat. No. 3,747,399, a pressure differential is created by a wick inserted in the end of the tube. The tube is in contact with the soil, causing moisture to be drawn into the tube, displacing and compressing the air in the tube so as to cause a pressure sensitive switch to operate. Such capillary activated systems are sensitive to clogging, are slow acting and deal in small pressure changes, which are unreliable.
The device of the Richards patent, U.S. Pat. No. 2,863,698, uses the water flow through the capillary pores of a ceramic cell to create a pressure differentiation in the cell to open a valve. The pressure created by the capillary action is small, and slow acting.
In U.S. Pat. No. 3,981,446, a column of water is used to control a valve. The size of the tube is such that the water does not flow out when open to air pressure. The valve is responsive to the pressure changes in the column of water. Once again, small pressure differentials are created.
The device shown in the patent to Parker, U.S. Pat. No. 2,215,132, uses the water flow through an outside household faucet attached to a venturi device to create suction for distributing liquid solutions in the water line. The Parker device is not used as a control for the flow of water through the system, but only to mix the liquid fertilizer with the water in the main water outlet.